1. Field of the Invention
The present disclosure relates to an optical pickup device having a structure in which a lens driving unit is mounted on a movable base, the lens driving unit including, for example, a lens holder and a focus correcting mechanism.
2. Description of the Related Art
An optical pickup device that reproduces information from various types of recording media, such as CDs or DVDs, includes a movable base that moves along a recording surface of a disk, with a lens driving unit being mounted on the movable base. The lens driving unit is provided with a unit chassis. A tilt adjusting mechanism that adjusts the tilt of the lens driving unit is provided between the unit chassis and the movable base.
In the lens driving unit, mounted at the unit chassis are a lens holder that holds an objective lens opposing a disk, a resilient supporting member that movably supports the lens holder, a focus correcting mechanism that moves the lens holder in a direction of an optical axis of the objective lens, and a tracking correcting mechanism that moves the lens holder in a radial direction that is orthogonal to the optical axis.
In an optical pickup device described in Japanese Unexamined Patent Application Publication No. 2001-319342 (Patent Literature (PTL) 1), four resilient wires that extend in a direction that is orthogonal to an optical axis of an objective lens are used as resilient supporting members. Base portions of the resilient wires are secured at a base member corresponding to a unit chassis. A lens holder is secured to end portions of the resilient wires. In this structure, by resiliently flexing the resilient wires, the lens holder is movable in a focus correction direction and a tracking correction direction.
The optical pickup device described in PTL 1 includes a stopper at a bottom portion of an optical chassis corresponding to the movable base. The stopper opposes a bottom portion of the lens holder through a through-hole formed in the base member. When the lens holder moves by a large amount in a direction opposite to a disk, the bottom portion of the lens holder passes through the through-hole and comes into contact with the stopper, to allow the amount of movement of the lens holder to be restricted.
Since the optical pickup device described in PTL 1 has a structure in which only the optical chassis opposes a lower portion of the lens holder, the optical pickup device can be made thin.
The optical pickup device described in PTL 1 has a structure in which the bottom portion of the lens holder and the stopper of the optical chassis come into contact with each other via the through-hole formed in the base member. Therefore, in a step that is executed after, for example, the resilient wires, the lens holder, and the focus correcting mechanism have been mounted on the base member and before the base member is mounted at the optical chassis, if an external force accidentally acts upon the lens holder, the resilient wires may become excessively bent due to the movement of the lens holder to a position where it passes the inside of the through-hole. If the flexing amount of the resilient wires at this time goes beyond a resilience region and exceeds a yield point, the resilient wires undergo plastic deformation and become defective wires that are incapable of functioning.
In contrast, if the aforementioned through-hole is not provided and a portion of the lens holder is caused to contact the base member when the lens holder is pushed by an external force, it is possible to prevent the resilient wires from flexing by an abnormally large amount. However, the use of such a structure gives rise to new problems such as those described below.
When the lens holder is to be mounted at the base member, it is desirable that the lens holder be secured to the resilient wires after an optical axis center of the objective lens held by the lens holder has been positioned with respect to the base member using an adjusting jig with the base portions of the resilient wires being secured at the base member first. Since the resilient wires are also used as energization paths to coils provided at the lens holder, in general, ordinarily the resilient wires and metallic terminals, which are mounted in the lens holder, are soldered to each other, and the resilient wires and the lens holder are secured to each other by the adhesive force of the solder.
Here, if, during the soldering, flux adheres to a surface of the base member, when a completed optical pickup device is used in a high-temperature environment, the flux is heated and becomes adhesive, as a result of which the lens holder tends to adhere to the surface of the base member by the flux.
In this type of optical pickup device, when a new disk has been loaded, while the focus correcting mechanism moves the lens holder by a large amount in a direction away from the disk and, from this position, moves the lens holder towards the disk, the objective lens causes detection light to converge on a recording surface of the disk and return light thereof is detected, so that, for example, detection of the presence or absence of the disk or detection of the disk type, such as a CD or DVD, is performed. During this operation, if the lens holder even temporarily adheres to the base member, an error occurs in the aforementioned detections. This causes an erroneous determination that the disk does not exist or malfunctions, such as a discharge of the disk to the outside of the optical pickup device without identifying the disk type.
In order to prevent the adhesion of flux to the base member, a method for mounting the resilient wires at the base member after soldering the resilient wires to the lens holder may be considered. However, when the resilient wires that are secured to the lens holder are to be mounted at the base member, it is difficult to position with high precision the optical axis of the objective lens held by the lens holder with respect to the base member.